KR101013494B1 - Recess waveguide microwave chemical plant for production of ethene from natural gas and the process using said plant - Google Patents

Abstract

A recess waveguide microwave chemical plant for producing ethene from natural gas and a process for producing ethene using the plant are disclosed. The installation comprises a recess waveguide (1), a mode converter and coupling orifice plate (2) provided on the left side of the recess waveguide (1), a short circuit plunger (3) provided on the right side of the recess waveguide (1) and the A chemical reactor 4 is provided across the recess waveguide 1.

Ethene, natural gas, recess waveguide, microwave, methane

Description

Recess waveguide microwave chemical plant for producing ethene from natural gas, and how to use the plant {RECESS WAVEGUIDE MICROWAVE CHEMICAL PLANT FOR PRODUCTION OF ETHENE FROM NATURAL GAS AND THE PROCESS USING SAID PLANT}

The present invention relates to a method for producing ethene from natural gas using a resonant cavity recessed waveguide microwave chemical plant, and the present invention relates to ethene from natural gas using a resonant cavity recessed waveguide microwave chemical plant. It belongs to the technical field of producing microwave technology.

Ethene is one of the most important basic raw materials in the chemical industry, which is also one of the largest production chemicals in the world. Ethene is the basic raw material for producing various organic chemicals and synthetic materials.

Current global industrial processes for producing ethene include mainly cracking diesel or naphtha at high temperatures. Large quantities of oil are consumed every year, and the ground's oil resources are decreasing day by day.

The world's natural gas reserves found are about 134 × 10 ¹² m3, and the number of recently discovered large natural gas reserves continues to increase. If natural gas is used to replace petroleum to produce ethene, the pressure on petroleum requirements can be significantly alleviated, and the development of the natural gas chemical industry can also be promoted.

Methane is the main component of dry natural gas (greater than 90%); For convenience, methane is sometimes referred to instead of natural gas from here until the end of the present invention.

In world-class laboratory studies, two conventional heating methods, indirect and direct methods, are used to convert methane to ethane. The indirect method described above consists of (1) ethene being produced from methane via methanol, or (2) ethene is produced from methane via synthesis gas. The former method is said to consume a lot of energy during gas production. There is a disadvantage, and the latter method has to solve the problem of how to suppress the regeneration of methane during the reaction process.

The most important problem in the direct method is the oxidative coupling of methane. In 1982, from UCC (US). this. G. E. Keller and M. M. M. M. Bhasin first published the result of ethene production through catalytic oxidative coupling of methane. Since then, researchers have been focusing on research mainly in two aspects: (1) finding high quality catalysts, and (2) improving reactors. Why. Jiang et al. Believe that ethene should have a single-pass yield that exceeds the 40% threshold in order for the production of ethene from methane to be economically viable. However, to date, the single pass yield of ethene is still less than 30%.

Thus, the production of ethene from methane through conventional heating methods is still in the research stage, and methods for achieving industrial production with good economic advantages are still unavailable.

Another method of producing ethene from methane is microwave chemistry, including plasma chemistry. This microwave chemical reaction has two significant advantages: (1) the chemical reaction rate is significantly improved; (2) Reactions that are difficult to carry out in terms of conventional thermodynamics can also be carried out relatively easily. Methane is the most stable organic molecule, and the reaction of producing ethene from methane through dehydrogenation coupling in the absence of oxygen can only be carried out at high temperatures of 1400 ° C. However, using microwave chemical methods, methane can be easily broken down into ethene. According to internationally published literature, the single pass yield of ethene has already reached 30%, which is higher than the single pass yield obtained with conventional heating methods, but the single pass yield is global for economic viability. It is still below the proven threshold of 40%.

Available microwave chemistry experiments are conducted mainly in rectangular waveguides, or in resonant cavities formed of rectangular waveguides, which are still limited to rectangular waveguides; Difficulties in producing ethene from methane (natural gas) by microwave chemical methods include:

(1) the volume of a small resonant cavity for microwave chemical reactions;

(2) low flow rates of the feed gas methane (natural gas);

(3) Single pass yield of less than 40% ethene.

Thus, to date, the technical background has three difficulties, including small co-volume, low methane flow rate, and low ethene single pass yield, although ethene is produced from methane (natural gas) by conventional heating or microwave chemical methods. The problem is that it must be solved continuously. This well-known problem worldwide has been intensively studied by many scientists for decades but is still unresolved.

Technical Difficulties : An object of the present invention to solve the above disadvantages in the art is to provide a resonant cavity-type recess waveguide microwave chemical plant for producing ethene from natural gas, and a method for producing the same for chemical industrial production. With the object of the present invention, ethene can be produced from natural gas with low cost and high efficiency.

Technical design : The resonant cavity-type recess waveguide microwave chemical plant for producing ethene from natural gas of the present invention comprises a recess waveguide, a mode converter and coupling orifice plate, an adjustable short-circuiting plunger (or fixed Short circuit plate), and a chemical reactor; Here, a recess waveguide is provided to the body, a mode converter and a coupling orifice plate are provided on the left side of the recess waveguide, and an adjustable shorting plunger (or fixed shorting plate) is provided on the right side of the recess waveguide, The reactor is located across the recess waveguide.

Such recess waveguides are referred to as circular recess waveguides, elliptical recess waveguides, rectangular recess waveguides, trapezoidal recess waveguides, V-shaped recess waveguides, or waveguides having any shape of cross section. A wedge shaped high power matching rod (dry rod or water rod) associated with the working wavelength is applied to the distal portion of the metal parallel flat plate at the two wing portions of the recess waveguide. The microwave working frequency of the recess waveguide is within 0.3 to 22 GHz. The recess waveguide can be operated in a continuous wave or a pulse wave.

The recess waveguide includes a left metal flat plate, a right metal flat plate, a wedge-shaped matching rod, an insulating strip, and a cutoff waveguide. The left metal flat plate and the right metal flat plate are symmetric in shape; Insulating strips are respectively arranged on both sides between the left metal flat plate and the right metal flat plate; The wedge-shaped mating rod is arranged inside the insulating strip; A space is formed between the left metal flat plate and the right metal flat plate; Through holes are arranged along the longitudinal direction of the flat plate at the centers of symmetry of the end faces of the left and right metal flat plates of the end faces of the recess waveguides.

For convenience, circular recess waveguides are employed as examples for describing various recess waveguides from here until the end of the specification herein.

The mode converter is used to convert the microwave input mode from the microwave source into the waveguide into the required microwave mode that meets the requirements of the recess waveguide. This can be accomplished by using a single stage converter, or a multi-stage transducer connected in series. The coupling orifice plate is used to couple the energy of the microwave source into the resonant cavity, which orifice plate can be disposed at the input end or the output end of the mode converter, or can be arranged between the multi-stage transducers. In order to perform the two functions mentioned above, a number of combination designs are available; Only one design is employed here as an example for explanation as follows.

The mode transducer and coupling orifice plate include a first transducer, a flange, a second transducer, and a coupling orifice plate. The first transducer described above is a rectangular waveguide to circular waveguide transducer. The second transducer comprises an upper insulating strip, a lower insulating strip, an upper wedge matched rod, a lower wedge matched rod, a left metal flat plate, and a right metal flat plate; Wherein the shape formed of the upper insulation strip, the lower insulation strip, the upper wedge matched rod, the lower wedge matched rod, the left metal flat plate, and the right metal flat plate is consistent with the recess waveguide. The central through hole connected to the recess waveguide is frustum shaped. The outer side of the central through hole of the frustum body is connected with the first transducer, the outer end of the first transducer is connected with the flange, and the coupling orifice plate is provided on the flange.

The shorting plunger is an important part of the resonant cavity, which has two forms: an adjustable shorting plunger or a fixed shorting plate. Here, the above-mentioned adjustable short circuit plunger is adopted as an example for explanation.

The adjustable shorting plunger includes a first shorting plunger metal plate, a second shorting plunger metal plate, a third shorting plunger metal plate, a first circular insulating gasket, a second circular insulating gasket, a hollow circular tube, a metal circular rod, a sleeve, and a metal A flat plate; Here, the first short plunger metal plate, the second short plunger metal plate, the third short plunger metal plate, the first circular insulated gasket, and the second circular insulated gasket are spaced apart from each other, the center of which is one end of the hollow circular tube. Fixed to the part; The other end of the hollow circular tube is disposed in the sleeve; The sleeve is fixed to the center of the metal flat plate; The metal circular rod is located in the middle of the hollow circular tube.

The chemical reactor comprises a reactor made of a low loss material, a top cover, a bottom cover, a gas inlet tube, a gas outlet tube, an exciter, and a Langmuir probe; Wherein the top cover, the gas inlet tube, the bottom cover, and the gas outlet tube are each located at both ends of the chemical reactor; The exciter is located in the middle of the chemical reactor; The Langmuir probe is arranged in a chemical reactor and fixed on the top cover.

The method for producing ethene from natural gas using the resonant cavity-type recess waveguide microwave chemical plant described above comprises the following steps:

(1) adopting a large-scale resonant cavity-type recess waveguide microwave chemical plant having a working frequency within 0.3 to 22 GHz;

(2) causing the resonant cavity-type recess waveguide microwave chemical plant to be in resonance and the reactor to be in vacuum;

(3) selecting hydrogen as auxiliary gas;

(4) adjusting the pressures of the feed natural gas and auxiliary hydrogen gas to 1 to 20 atm, and introducing these gases separately into the reactor via different flowmeters for metering flow rates of different gases;

(5) adopting a flow rate ratio of feed natural gas and auxiliary hydrogen gas, that is, a ratio of natural gas: hydrogen gas, from 50: 1 to 1:20;

(6) mixing a feed natural gas and an auxiliary hydrogen gas in a gas mixture cabinet and introduce it through a feed gas inlet and a top cover into a quartz reactor of a resonant cavity-type recess waveguide microwave chemical plant;

(7) adjusting the total pressure of the mixed gas in the quartz reactor to 1 × 10 ⁻⁴ to 20 atm and making the total pressure of the mixed gas in the quartz reactor slightly lower than the pressure of the feed natural gas and auxiliary hydrogen gas;

(8) Turn on the power of the microwave source, adjust the microwave output power from tens of watts to several hundred kilowatts according to the auxiliary gas type, flow rate ratio, and gas mixture pressure, and discharge the gas mixture in the quartz reaction tube to generate a microwave plasma. Wherein the discharge condition can be recognized from the Langmuir probe and the cutoff waveguide;

(9) thereafter, finely adjusting the microwave output power to obtain the required product, wherein the liquid ethene, which is the required product, can be collected in a condensation trap.

The present invention is designed according to electromagnetic field theory, microwave technology, plasma technology, and chemical engineering principles. The resonant cavity-type recess waveguide microwave chemical plant for producing ethene from natural gas is shown in FIG. 1. The principle of operation is as follows: microwaves from the power source are input into the recess waveguide resonant cavity described above through the circulator, the directional coupler, and the coupling orifice plate, and the reaction tube of the chemical reactor follows the two wing portions thereof. Formed through the sett waveguide, the resonant cavity is allowed to be in resonance; Natural gas flows from one end of the reaction tube into the resonant cavity described above, free electrons acquire energy under the action of microwave electromagnetic fields and inelastically collide with methane and hydrogen molecules to generate more electrons, and newly generated freedom The electrons regain energy and collide with methane and hydrogen molecules to generate more electrons, causing an avalanche, where the free electrons are gas decomposed and discharged to produce an overall electrically neutral plasma. As the situation increases. High energy electrons decompose C-H bonds of methane molecules and H-H bonds of hydrogen molecules through inelastic collisions, generating a number of free radicals with active chemical properties; The product is produced through various combinations of these, and the composition of the product is confirmed by gas chromatography. The resulting ethene exits the resonant cavity and flows along the chemical reaction tube into the condensation trap.

For convenience of explanation, the invention is divided into two parts: (1) a resonant cavity-type recess waveguide microwave chemical plant as shown in FIG. 2; (2) It is explained that ethene is produced from natural gas by using the recess waveguide microwave chemical equipment of the resonant cavity type. The detailed description is as follows:

1. Resonant cavity type Recess wave-guide  Microwave chemical equipment

(One) Recess wave-guide

The recess waveguide refers to a circular recess waveguide, an elliptical recess waveguide, a rectangular recess waveguide, a trapezoidal recess waveguide, a V-shaped recess waveguide, or a waveguide having an arbitrary cross section. A wedge-shaped high power matching rod (dry rod or water rod) associated with the working wavelength is applied to the distal portion of the metal parallel flat plate in the two wing portions of the recess waveguide. The microwave working frequency of the recess waveguide is within 0.3 to 22 GHz, and various acceptable commercial or industrial frequencies such as 0.434 GHz, 0.915 GHz, 2.45 GHz, or 5.80 GHz can be adopted worldwide. The recess waveguide can be operated in continuous or pulsed wave, which can also be operated at low or high power. For convenience of description, a circular recess waveguide is adopted as an example for detailed description.

The circular recess waveguide uses two metal flat plates spaced by the upper and lower insulating strips, with a wedge-shaped mating rod (dry rod or water rod) fitted inside the insulating strip. The height of the wedge is an integral multiple of the working wavelength of the electromagnetic wave. Circular through holes having a diameter of D ₀ are arranged in the center of symmetry of the end faces of the two metal flat plates along the longitudinal direction of the flat plate, as shown in FIGS. 2 and BB. The axial direction of the circular hole is the propagation direction of the electromagnetic wave, which is simply called the axial direction. The wedge-shaped mating rods of the high frequency recess waveguide are blow molded from quartz glass into the desired shape, and as shown in FIG. 3, the rods have tubes into which water enters and exits. The rod may be another type of matched water rod. The recess waveguide insulation strip is made of a ceramic material as shown in FIG. 3. If a dry rod is employed, the shape and size shown in FIG. 3 is also used. A plasma spectrum observation hole is formed on the sidewall of the through hole of the recess waveguide. The cutoff waveguide is fitted on the outside of the hole, and the microwave energy leaked from the hole is below the national standard. This hole must ensure that through this hole the light formed by the plasma inside the quartz reaction tube can be identified and the plasma temperature or spectrum formed by the plasma can be measured.

(2) mode  Transducer and Coupling Orifice  plate:

In order to perform two functions, namely mode switching and energy combining, a number of combination designs are available, where only one design is employed for illustration. The mode transducer and coupling orifice plate comprise a first transducer, a second transducer, a flange and a coupling orifice plate. The first transducer is a rectangular waveguide to circular waveguide transducer. The second transducer is a circular waveguide to circular recess waveguide transducer. The first transducer has one end having a cross section of a rectangular waveguide, and the other end having a cross section of a circular waveguide, where the transition region between them, ie all points on the rectangular perimeter and corresponding points on the circumference, is straight The space formed by connecting with is straight. The second transducer has one end having a cross section of a circular waveguide and the other end having a cross section of a circular recess waveguide having a different diameter. The distance of the two points of the V-shaped maximum opening formed by extending from the vertical centerline of one end of the V-shaped circular cross section is equal to the distance between two metal flat plates of the circular recess waveguide. A connection hole is formed on the waveguide wall at the end of the circular recess waveguide. A rectangular waveguide flange is fitted on the cross-sectional end of the rectangular waveguide. A coupling orifice plate is arranged on the flange, which is inductive or capacitive and can be round, rectangular or otherwise shaped. The coupling orifice plate is also connected with the input waveguide to couple the microwave energy into the resonant cavity.

(3) adjustable short circuit plunger :

The shorting plunger is an important part of the resonant cavity, which can take two forms: an adjustable shorting plunger or a fixed shorting plate. Here, as an example for explanation, an adjustable short plunger is adopted.

The circular recess waveguide has one end connected with the mode converter and coupling orifice plate, and the other end equipped with an adjustable shorting plunger to form a resonant cavity. The adjustable shorting plunger is formed by a metal flat plate having the same shape as the shape of the hollow pattern of the waveguide end face, which can be made of the same material as the waveguide material, the plunger having a thickness of 1/4 wavelength. . There is a gap between the metal flat plate and the waveguide to space them apart; The metal flat plate of the shorting plunger may be formed in one or more pieces. An insulating gasket having a thickness of 1/4 wavelength is used to space the metal flat plate. The insulating gasket has a diameter slightly smaller than the diameter D ₀ of the recess waveguide through-hole, is made of ceramic material and is fixed on the hollow circular tube. A metal circular rod whose diameter is equal to the diameter of the hollow circular tube is disposed in the hollow circular tube. The end face of this circular tube, the end face of the circular rod, and the first metal flat plate are in the same plane. The hollow circular tube passes through the sleeve; This sleeve passes through the hole at the symmetric center of the metal flat plate of the end face of the recess waveguide and is fixed thereon. The hollow circular tube is connected with a mechanical control mechanism, causing the shorting plunger to move in parallel in the recess waveguide.

(4) chemical reactor:

Since the chemical reactor is a place where microwaves and reactants react, this chemical reactor should be located inside the resonant cavity of the circular recess waveguide. The reactor may be made of quartz, ceramic, low loss glass, or other nonmetallic solid material with low loss in electromagnetic fields, but is preferably made of transparent quartz to easily identify the spectrum formed by the plasma. The chemical reactor may be in the form of a circular tube or other form as desired, where the reactor form should help to carry out the chemical reaction, and the chemical reactor should be able to be accommodated in the resonant cavity of the recess waveguide, The reactor should be able to be equipped with an inlet tube for the feed gas and a gas outlet tube for the product.

The excitation group is arranged in a chemical reactor, which may be a metal excitation group, a nonmetallic excitation group (including semiconductors), or a mixed excitation group of a metal-nonmetal. Suitable materials for the metal exciter include tungsten, iron, nickel, or alloys thereof. Suitable materials for the nonmetallic excitation group are graphite. The size and shape of the exciter is related to the working frequency of the microwave source.

The Langmuir probe is arranged in a chemical reactor to measure the parameters of the plasma. The probe may be one, two or many. For example, two Langmuir probes are inserted into the plasma, and a voltage is applied to the current passing through the probe to provide a current-voltage characteristic curve, and as a result, the measured plasma density or electron temperature and the The same various parameters are obtained.

The probe may be made of a metallic material that is resistant to high temperatures, which is usually located within the flat plate region of the recess waveguide to avoid the effects on microwave discharges and chemical reactions while measuring plasma parameters.

In total, a resonant cavity-type recess waveguide microwave chemical facility is formed by assembling a recess waveguide, a mode converter and coupling orifice plate, an adjustable shorting plunger (or fixed shorting plate), and a chemical reactor according to FIG. 2.

2. Resonant cavity type Recess wave-guide  From natural gas using microwave chemical equipment Ethen  production

The method for producing ethene from natural gas by using the resonant cavity-type recess waveguide microwave chemical plant described above comprises the following steps:

(1) adopting a large-scale resonant cavity-type recess waveguide microwave chemical plant having a working frequency within 0.3 to 22 GHz, wherein the microwave source can adopt continuous or pulsed waves;

(2) leaving the resonant cavity-type recess waveguide microwave chemical plant in resonance and the reactor in vacuum;

(3) selecting a suitable auxiliary gas, wherein hydrogen gas is used as the auxiliary gas;

(4) adjusting the pressures of the feed methane (natural gas) and auxiliary hydrogen gas to 1 to 20 atm, and introducing these gases separately into the reactor through different flowmeters for metering flow rates of different gases;

(5) adopting a flow rate ratio of feed methane (natural gas) and auxiliary hydrogen gas, that is, a ratio of natural gas: hydrogen gas, from 50: 1 to 1:20;

(6) mixing feed methane (natural gas) and auxiliary hydrogen gas in a gas mixture cabinet and introducing it through a feed gas inlet and a top cover into a quartz reaction tube of a resonant cavity-type recess waveguide microwave chemical plant;

(7) adjusting the total pressure of the mixed gas in the quartz reaction tube to be slightly lower than the pressure of feed methane (natural gas) and auxiliary hydrogen gas;

(8) operating a power source of the microwave source, adjusting the microwave output power, and discharging the gas mixture in the quartz reactor to produce a microwave plasma, wherein the discharge condition can be perceived from a Langmuir probe and a cutoff waveguide ;

(9) thereafter, finely adjusting the microwave output power to obtain the required product, wherein liquid ethene, which is the required product, can be collected in the condensation trap.

Important factors to ensure high single pass yield in the production of ethene from methane (natural gas) include choice of resonant cavity-type recess waveguide microwave chemical plants, microwave power strength, gas pressure, and mixing with methane (natural gas) Variety of gases (eg hydrogen gas), and ratios of flow rates of methane (natural gas) and auxiliary hydrogen gas.

Principle of operation : electrons in a microwave electromagnetic field acquire energy; When high-energy electrons collide inelastically with gas molecules, ionization of methane and hydrogen molecules is induced, producing an overall electrically neutral plasma. CH bonds of methane molecules and HH bonds of hydrogen molecules decompose through inelastic collisions of high-energy electrons to generate free radicals; These free radicals are very active and they can be recombined in certain ways to form new substances such as ethene. This is the principle of the conversion of ethene from natural gas (methane), and it can be seen from this principle that it is very important to create a suitable environment that can provide strong electromagnetic energy; The resonant cavity-type recess waveguide microwave chemical plant of the present invention may meet the above mentioned requirements.

Advantages of the invention:

(1) Currently, ethene production uses petroleum as a raw material, but due to its long-term mining, global petroleum resources are decreasing day by day. The production of ethene from natural gas instead of petroleum provides new access to raw materials, which can significantly reduce the pressure on petroleum demand. In addition, global natural gas resources are relatively abundant.

(2) The present invention can be used in areas with abundant natural gas resources, and the present invention also has the advantages of low investment, quick installation and low cost, which is the cost of the downstream product using ethene as raw material It can promote reduction and improve competitiveness in the global market.

(3) The present invention is environmentally friendly. The production of ethene from natural gas by the microwave method involves no harmful substances in the feed materials, production processes and products. The whole production process is clean production.

(4) The present invention is advantageous for the development of the natural gas chemical industry.

(5) Compared with other waveguide structures in the microwave technology field, recess waveguides have a large size advantage, and only the present invention can be applied to the industrial production of ethene.

(6) The present invention does not require any catalyst.

1 is a block diagram for the production of ethene from natural gas using a resonant cavity-type recess waveguide microwave chemical plant.

2 is a front and cross-sectional view of a resonant cavity-type recess waveguide microwave chemical plant.

3 is a side view of a resonant cavity-type recess waveguide microwave chemical plant.

4 is a BB cross-sectional view of a resonant cavity-type recess waveguide microwave chemical plant.

5 is a CC cross-sectional view of a resonant cavity-type recess waveguide microwave chemical plant.

6 is a horizontal cross-sectional view of a resonant cavity-type recess waveguide microwave chemical plant.

7 is an AA cross-sectional view of a resonant cavity-type recess waveguide microwave chemical plant.

8 is a 3D image of the recess waveguide wedge-shaped matching rod and insulation strip, FIG. 8A is a 3D image of the wedge-shaped matching rod, and FIG. 8B is a 3D image of the insulation strip.

9 is a 3D image of a mode converter.

* Brief description of symbols for the main parts of the drawings *

1: recess waveguide

11: left metal flat plate

12: Right metal flat plate

13: wedge mating rod

14: insulation strip

15: cutoff waveguide

2: mode transducer and coupling orifice plate

21: first converter

23: second converter

231: top insulation strip of the second mode converter

232: lower insulation strip of the second mode converter

233: Upper wedge mating rod of second mode transducer

234: Lower wedge mating rod of second mode transducer

235: left metal flat plate of the second mode converter

236: Right metal flat plate of the second mode converter

3: adjustable short circuit plunger

31: first short plunger metal plate

32: second short circuit plunger metal plate

33: third paragraph plunger metal plate

34: first circular insulating gasket

35: second circular insulating gasket

36: hollow circular tube

37: metal round rod

38: sleeve

39: metal flat plate

4: chemical reactor

41: reactor

42: top cover

43: bottom cover

44: with

45: Langmuir probe

46: gas inlet pipe

47: gas outlet pipe

D ₀ : Diameter of circular recess waveguide through hole

D ₁ : Diameter of the outer end of the frustum through-hole

D ₂ : Diameter of chemical reactor

L ₀ : Length of circular recess waveguide

L ₁ : Length of the first transducer

L ₂ : Length of second transducer

H: Overall height of recess waveguide

H ₁ Height of recess waveguide insulation strip

H ₂ Base height of wedge-shaped mating rod in recess waveguide

H ₃ Height of wedge

W ₁ Width of wedge-shaped mating rod in recess waveguide

W ₂ Distance between parallel flat plates of recess waveguide

For convenience of explanation, the present invention is described in two parts: (1) The first part includes implementing a resonant cavity-type recess waveguide microwave chemical plant. (2) The second part includes the execution of ethene production from natural gas using a resonant cavity-type recess waveguide microwave chemical plant.

1) resonant cavity type Recess wave-guide  Implementation of microwave chemical plant

The resonant cavity-type recess waveguide microwave chemical plant comprises a recess waveguide 1, a mode converter and coupling orifice plate 2, an adjustable short circuit plunger 3, and a chemical reactor 4, the recess as the body. Having a waveguide 1, the mode converter and coupling orifice plate 2 is mounted on the left side of the recess waveguide 1, and an adjustable short circuit plunger 3 is mounted on the right side of the recess waveguide 1 The chemical reactor 4 is mounted opposite the recess waveguide 1.

The recess waveguide 1 comprises a left metal flat plate 11, a right metal flat plate 12, a wedge-shaped matching rod 13, an insulating strip 14, and a cutoff waveguide 15. The left metal flat plate 11 and the right metal flat plate 12 are symmetrical, and the insulating strips 14 are disposed on two sides between the left metal flat plate 11 and the right metal flat plate 12, respectively. , The wedge-shaped mating rod 13 is disposed on the inner surface of the insulating strip, a space is formed between the left metal flat plate and the right metal flat plate, the through hole of the recess waveguide 1 is the left and right metal planes of the recess waveguide It is arranged along the longitudinal direction of the flat plate at the center of symmetry of the plate end face.

The mode transducer and coupling orifice plate 2 comprises a first transducer 21 and a second transducer 23. The first transducer 21 is a rectangular waveguide compared to the circular waveguide transducer. The second transducer 23 includes an upper insulating strip 231, a lower insulating strip 232, an upper wedge matched rod 233, a lower wedge matched rod 234, a left metal flat plate 235, and a right metal. Plate 236, upper insulating strip 231, lower insulating strip 232, upper wedge mating rod 233, lower wedge mating rod 234, left metal flat plate 235, right metal The shape formed by the flat plate 236 coincides with the recess waveguide. The through hole in the center connected to the recess waveguide 1 is in the shape of a frustum. The outer surface of the central through hole of the frustum body is connected to the first transducer 21.

The adjustable shorting plunger 3 includes a first shorting plunger metal plate 31, a second shorting plunger metal plate 32, a third shorting plunger metal plate 33, a first circular insulating gasket 34, a circular insulating gasket (35), hollow circular tube (36), metal circular rod (37), sleeve (38) and metal flat plate (39), wherein first short plunger metal plate (31), second short plunger metal The plate 32, the third shorting plunger metal plate 33, the first circular insulating gasket 34, and the second circular insulating gasket 35 are spaced apart from each other, the center of which is the end of the hollow circular tube 36. The other end of the hollow circular tube 36 is disposed in the sleeve 38, the sleeve 38 is fixed to the center of the metal flat plate 39, and the metal circular rod 37 is a hollow circular tube. It is in the middle of 36.

The chemical reactor 4 comprises a reactor 41 made from a low-loss material, a top cover 42, a bottom cover 43, an exciter 44, a Langmuir probe 45, a gas inlet pipe 46 and A gas outlet tube 47, wherein the top cover 42, the gas inlet tube 46, the bottom cover 43, and the gas outlet tube 47 are each at two ends of the chemical reactor 41. , The exciter 44 is located in the middle of the chemical reactor 41, the Langmuir probe 45 is mounted in the chemical reactor 41, and is fixed to the top cover 42.

(One) Recess wave-guide

Here, the circular recess waveguide is described as an example. There are several manufacturing methods using sheet presses, such as machining and compression molding. For convenience of description, the following method will be used. The present invention can be made with the design shown in BB of FIG. 2, and the manufacturing method of the recess waveguide 1 is as follows. Two metal flat plates made of good conductors, for example copper, brass and aluminum alloys, are machined to the same size, where the length of the flat plate is determined according to the practical requirements as long as the process allows, and the height of the flat plate H and width W are related to the working wavelength (λ), H = 10λ-30λ, W = 0.35λ-1.26λ, and both edges of the metal flat plate are fixed by screws, and the center line of the boundary line where the two flat plates meet respectively in the lower surface and the upper end face along the longitudinal direction by using the (H ₁ + H ₂₎ = height of 0.15λ-1.5λ, W ₁ = W ₂ + 2 W ₃ Milling slots having a width of 0.5λ-2.313λ, the length of the slot being equal to the length L ₀ of the circular recess waveguide, where H ₁ = 0.1λ-1λ, H ₂ = (1/2 ) H ₁ , W ₂ = 0.4λ-1.313λ, W ₃ = 0.05λ-0.5λ, and boring is performed so that the through hole has a diameter D ₀ = 0.62λ-2.02λ at the center of symmetry of the end face along the longitudinal direction. When the screw is removed, each metal flat plate has a milled slot of width W ₅ = (1/2) W ₂ on one side. The two metal plane plates processed are the metal plane plate 11 on the left side of the recess waveguide shown in BB of FIG. 2 and the metal plane plate 12 on the right side.

The wedge-shaped mating rod 13 of the recess waveguide 1 is a main part that absorbs electromagnetic waves transmitted to the edges of the metal flat plate to reduce the leakage of microwaves. The height of the wedge is an integer multiple of 1/2 of the wavelength of the electromagnetic wave used, and H ₃ = 0.5λ-3λ. The wedge-shaped mating rod is fitted to the inner side of the insulating strip 14. The upper and lower insulating strips are used to adjust the gap between the left metal flat plate 11 and the right metal flat plate 12, have the same length as the circular recess waveguide, and may be made of an insulating material such as ceramic. The insulating strip has holes for gas inlet and outlet into the chemical reactor and holes for water inlet and outlet to the wedge mating rod. When the power is weak, a wedge-shaped matched dry rod can be used, which is of the same size and shape as the water rod and is made of a material (graphite) that can strongly absorb microwaves.

In FIG. 2, H ₄ = 0.05λ-0.5λ and W ₄ = 0.45λ-1.364λ.

The plasma spectrum observation hole is open in the side wall of the through hole of the recess waveguide 1, and the diameter of the hole is within 0.05λ-0.1λ. A cutoff waveguide 15 having an attenuation value within 100-200 db is adapted to fit outside of the hole, as shown in AA of FIG. 2. Microwave energy exiting the hall is lower than the national standard. The hole should be made to observe the light generated by the plasma in the quartz reaction tube and to measure the temperature of the plasma or the spectrum generated by the plasma.

(2) mode  Coupling with transducer Orifice  plate

The mode converter and coupling orifice plate 2 are shown in FIG. 2 and implemented in two parts. The manufacture of the first transducer 21 is performed by preparing a wax mold having the size of the rectangular waveguide end selected according to the frequency of use of the microwave source and the diameter of the circular waveguide end of D ₁ = 0.6λ-0.9λ, Connect the corresponding points on both ends with straight lines, match the copper waveguides using electrocasting techniques, melt the wax mold and polish the surface, fit the flange 22 to the rectangular waveguide ends, and round the waveguide ends Base boring, and fixed to the second transducer using screws, wherein the total length of the first transducer is L ₁ = 1λ-3λ. The manufacture of the second transducer 23 selects two metal plane plates (copper, brass, aluminum alloy) having a length of L ₂ = 1λ-3λ, and the overall width of the two metal plane plates is 2W = 0.35λ-1.26. λ, the overall height is H = 10λ-30λ, using the screws to fix the corners of the two metal flat plates, inside the hole has one diameter D ₁ = 0.6λ-0.9λ at the center of symmetry of the end face, A frustum with the other end having a diameter of D ₀ = 0.62λ-2.02λ equal to the diameter of the circular recess waveguide through-hole, where λ is the wavelength, is removed and the screw is separated into two pieces. A wedge-shaped groove is excavated in one side of the slot of each metal flat plate, where the height of the wedge is equal to the length L ₂ of the metal flat plate, the bottom of the wedge is rectangular, and the length of the long side of the groove is metal It should be equal to the height H of the flat plate and the length of the shorter side is W ₅ = (1/2) W ₂ = 0.2λ-0.656λ, and the machined surface should be smooth. Using a ceramic insulating material, two small ceramic wedges are processed, the upper insulating strip 231 and the lower insulating strip 232 of the second transducer, where the height of the ceramic wedge is equal to the length L ₂ of the metal flat plate. The bottom of the ceramic wedge is also rectangular, and the length of the long side of the wedge is W ₂ = 2W ₅ , The shorter length is set to H ₁ = 0.1λ-1λ. Each of the upper / lower wedge matched rods 233, 234 of the second transducer is fitted to the inner side of the upper / lower insulation strips 231, 232 of the second transducer, which is similar to the wedge-shaped match rods in the recess waveguide. It is a water rod or a dry rod, where the height of the wedge is H ₃ . The upper and lower ceramic insulation strips are placed between the left metal flat plate 235 and the right metal flat plate 236 of the second transducer, such as a mating rod, screwed together, the circular recess waveguide 1 and the mode transducer. Connect (2).

The shape of the coupling orifice plate 24 is the same size as the flange of the selected standard rectangular waveguide and the thickness is 0.005λ-0.1λ. If the circular hole is open at the center of symmetry, the diameter of the hole is less than or equal to the height of the rectangular waveguide, and if the rectangular coupling hole is open at the center of symmetry, the rectangular hole is less than or equal to the width of the rectangular waveguide and the height is rectangular waveguide Is less than or equal to the height of. If the coupling orifice plate has narrow slits in a direction parallel to the width direction, a capacitive diaphragm is formed. If the coupling orifice plate has narrow slits in a direction parallel to the height direction, an inductive diaphragm is formed. The coupling orifice may be circular, rectangular or other shaped. The size of the slit and orifice can be optimized by measurement.

(3) adjustable short circuit plunger

The adjustable shorting plunger 3 is formed of a metal plate having the same shape as that of the hollow pattern of the distal face of the recess waveguide 1. For example, the first short plunger metal plate 31, the second short plunger metal plate 32, the third short plunger metal plate 33, and the applied raw material may be copper, brass, aluminum alloy. The thickness of the short metal plate is 1/4 wavelength. The through hole is made in the center of the shorting plunger metal plate so that the plunger fits into the hollow circular tube 36. Metal flat plates and waveguides are spaced at regular intervals. The first circular insulating gasket 34 and the second circular insulating gasket 35 having a thickness of 1 / 4λ are disposed between the shorting plunger metal plates to be separated. The diameter of the gasket is 0.8 times the diameter D ₀ of the through hole of the recess waveguide. The first shorting plunger metal plate 31, the first circular insulated gasket 34, the second shorting plunger metal plate 32, the second circular insulated gasket 35, and the third shorting plunger metal plate 33 are short-circuited. In order to prevent random movement of the metal plate, it is sequentially fitted to the hollow circular tube 36 so that the outer diameter of the short metal plate and the hollow circular tube is tightly fitted. The metal circular rod 37 is disposed in the hollow tube 36, and the diameter of the rod is the same as that of the hollow circular tube. The circular tube end face, the circular rod end face and the first short plunger metal plate 31 are arranged in the same plane.

The metal flat plate 39 is mounted to the end face of the recess waveguide 1. One hole is drilled in the center of symmetry of the plate, and the sleeve 38 passing through the hole is fixed to the metal flat plate 39. The hollow circular tube 36 of the shorting flanger part passes through the sleeve 38 and is placed in the slide in a fixed state. The hollow circular tube 36 is connected with a mechanical adjustment mechanism to move the shorting plunger 3 in parallel in the recess waveguide 1.

(4) chemical reactor

The reactor 41 is made from low-loss materials such as quartz, high quality ceramics or nonmetallic materials that do not absorb microwaves. The reactor 41 made from the low-loss material can be of any shape that can be equipped by a circular tubular or resonant cavity. The following examples will be described to illustrate the implementation of chemical reactors.

The reactor 41, made of low-loss material, is made of a round tubular form of quartz. The diameter of the reactor is the distance W ₂ between the parallel flat plates of the recess waveguide 1 as shown in FIG. Diameter D ₂ to be shorter. The height of the reactor is made somewhat higher than the overall height of the recess waveguide 1. The reactor 41 has one end fitted with a vacuum-proof top cover 42, which is connected to the supplied gas inlet 46. The other end of the reactor 41 is fitted with a vacuum-proof bottom cover 43. The bottom cover is connected to the production gas outlet 47 and more sequentially to the condensation trap and the vacuum pump.

The exciter 44 is arranged in a quartz round tube reactor 41. The excitation group can be made from iron, tungsten, or other non-metallic materials such as high temperature resistant metals or graphite. The exciter can be in any form that is advantageous for gas evolution. The Langmuir probe 45 is placed in a reactor 41 made of a low-loss material, placed in the 1λ-3λ position above the center circular through hole of the recess waveguide, and fixed to the top cover 42.

The previously mentioned parts are assembled according to FIGS. 2 and 1 to make a resonant cavity-type recess waveguide microwave chemical plant and the assembly includes:

(1) removal and washing of machine oil in each part;

(2) According to FIG. 2, the first short plunger metal plate 31, the second short plunger metal plate 32, the third short plunger metal plate 33, the first circular insulation gasket 34, and the second circular insulation Assembling each part of the shorting plunger 3 including assembling the gasket 35, the hollow circular tube 36 and the metal circular rod 37;

(3) Short metal plunger 11 of the left metal flat plate 11, the right metal flat plate 12, the wedge-shaped mating rod 13, the insulating strip 14, and the recess waveguide 1 according to FIG. 2. Arrangement, screwing, and preservation of corresponding holes on the insulating strip through the chemical reactor of the circular tube;

(4) connection of the first mode converter 21 and the second mode converter 23, the other end of the second mode converter 23 to the recess waveguide, and the other end of the first mode converter 21 Fixed to the waveguide flange 22, connecting the other end of the rectangular waveguide flange 22 to the coupling diaphragm 24;

(5) A metal circular plate (39) having a sleeve (38) is fixed to the other end of the recess waveguide (1) by a screw, so that the hollow circular tube (36) of the short circuit plunger (3) is a metal flat plate ( Allows the short circuit plunger 3 to be movable in the recess waveguide 1 in parallel without passing through the sleeve 38 of 39 and in connection with the mechanical adjustment mechanism;

(6) placement of exciter 44 into reactor 41;

(7) According to FIG. 2, the reactor 41 passes through one wing of the recess waveguide 1 and extends out of the recess waveguide from the other wing of the recess waveguide 1, and one end of the reactor 41. Fit the vacuum-proof top cover 42 to the part, connect feed gas inlet 46 to the top cover 42, vacuum-proof bottom cover 43 at the other end of the reactor 41 The bottom cover to the production gas outlet 47;

(8) According to FIG. 1, a flow meter is used to connect the feed gas inlet pipe 46 on the top cover 42 to the natural gas pipeline (or methane cylinder) and through the condensate trap above the bottom cover 43. The production gas outlet pipe 47 of the vacuum pump;

(9) According to FIG. 2, the Langmuir probe 45 is inserted into a desired position through a hole retained on the top cover 42, and fixed to the top cover 42 while maintaining the airtightness of the connection portion;

(10) According to FIG. 2, the cutoff waveguide 15 is connected to the viewing hole of the left metal flat plate 11 of the recess waveguide;

(11) connecting the microwave source with the coupling diaphragm 24 via the circulator and the directional coupler, connecting the power indicator to the two secondary arms of the directional coupler, and adjusting the shorting plunger to create a resonant cavity in a resonant state;

Thus, the resonant cavity-type recess waveguide microwave chemical plant for the production of ethene from natural gas is fully assembled and ready for use.

Resonant cavity type Recess wave-guide  From microwave gas using microwave chemical equipment Ethen  The production process includes:

(1) the adoption of large scale resonant cavity-type recess waveguide microwave chemical equipment essential for obtaining high single pass ethene from natural gas; Here, the operating frequency is 0.3-22 GHz and the microwave source may adopt continuous or pulsed waves.

(2) placing the resonant cavity-type recess waveguide microwave chemical plant in a resonant state and placing the reactor 41 in a vacuum state;

(3) the selection of a suitable auxiliary gas; Hydrogen gas is selected here as auxiliary gas.

(4) regulating the pressures of the feed methane (natural gas) and auxiliary hydrogen gas to 1-20 atm and feeding these gases into the reactor respectively through different flowmeters for measuring the flow rates of different gases;

(5) adopting feed methane (natural gas) and auxiliary hydrogen gas flow rate ratios such that the ratio of methane / hydrogen gas is 50: 1-1: 20;

(6) Mixing feed methane (natural gas) and auxiliary hydrogen gas in a gas mixing cabinet and through the feed gas inlet pipe 46 and the top cover 42 to the quartz reaction tube of the resonant cavity-type recess waveguide microwave chemical plant. Introduction;

7, the quartz reaction tube, the total pressure of the mixed gas 1x10 ^-4 - adjusted to adjusted to 20 atm, a little lower than the pressure of the total pressure of the mixed gas in the quartz reaction tube, the feed methane (natural gas) and auxiliary hydrogen gas;

(8) Turn on the microwave source, adjust the microwave effluent power from tens of watts to several hundred kilowatts according to the type of auxiliary gas, flow rate, and pressure of the mixed gas, and discharge the mixed gas in the quartz reaction tube to discharge the microwave plasma. Where the discharge conditions are known from Langmuir probes and cutoff waveguides;

(9) Next, finely adjust the microwave output power to obtain the desired product. In the above, the desired liquid ethene product can be collected in a condensation trap.

Key elements to ensure a high single pass yield of ethene production from methane (natural gas) are the choice of controlled resonant cavity-type recess waveguide microwave chemicals, the power of microwaves, gas pressure, mixed with methane (natural gas) Variety of gases (eg hydrogen) and flow rate ratios of methane (natural gas) and auxiliary hydrogen gas.

Two embodiments are described next. Even when the working pressures are the same, different products can be obtained under different input power (continuous wave) and different methane / hydrogen ratios. This proves that the change in parameters has a significant effect on the product.

Example  One From methane Ethen  production

Methane: Hydrogen = 23 L / min: 1.5 L / min

Working pressure = 1 atm

Input power = 4.2 KW (continuous wave)

Reaction result

Methane single pass conversion rate: 99.58%

Ethene single pass yield: 98.53%

Ethene single pass selectivity: 98.945%

Example  Production of ethane from 2 methane

Methane: hydrogen = 23 L / min: 0.7 L / min

Working pressure = 1atm

Input power = 4.0 KW (continuous wave)

Reaction result

Methane single pass conversion rate: 96.5%

Ethane single pass yield: 96.4%

Ethane Single Pass Selectivity: 99.9%

Conclusion: Ethene and ethane can be obtained by the resonant cavity-type recess waveguide microwave chemical plant of the present invention under various working parameters such as input power, methane / hydrogen ratio, and working pressure.

Claims (8)

In a resonant cavity-type recess waveguide microwave chemical plant for producing ethene from natural gas, The chemical plant is formed of a recess waveguide (1), a mode converter and coupling orifice plate (2), an adjustable short circuit plunger (3), and a chemical reactor (4), The recess waveguide 1 is provided to the main body, the mode converter and coupling orifice plate 2 is provided on the left side of the recess waveguide 1, and the adjustable shorting plunger 3 is provided with the recess waveguide ( Provided on the right side of 1), characterized in that the chemical reactor 4 is located across the recess waveguide 1, Resonant cavity-type recess waveguide microwave chemical plant. The method of claim 1, The recess waveguide 1 is a circular recess waveguide, an elliptical recess waveguide, a rectangular recess waveguide, a trapezoidal recess waveguide, a V-shaped recess waveguide, or a waveguide having an arbitrary cross section, The microwave working frequency of the recess waveguide 1 is within 0.3 to 22 GHz, characterized in that the recess waveguide 1 can be operated in continuous or pulsed waves, Resonant cavity-type recess waveguide microwave chemical plant. The method according to claim 1 or 2, The recess waveguide 1 comprises a left metal flat plate 11, a right metal flat plate 12, a wedge-shaped matching rod 13, an insulating strip 14 and a cutoff waveguide 15, The left metal flat plate 11 and the right metal flat plate 12 are symmetric in shape, and the insulating strip 14 is formed on both sides between the left metal flat plate 11 and the right metal flat plate 12. Respectively arranged in the inner side of the insulating strip 14, a space is formed between the left metal flat plate and the right metal flat plate, and the recess waveguide ( Characterized in that the through-holes 16 are arranged along the longitudinal direction of the flat plate at the symmetric centers of the left and right metal flat plates 11, 12 of the distal face of 1), Resonant cavity-type recess waveguide microwave chemical plant. The method of claim 1, The mode transducer and coupling orifice plate 2 comprises a first transducer 21 and a second transducer 23, The first transducer 21 is a rectangular waveguide to circular waveguide transducer, and the second transducer 23 is an upper insulation strip 231, a lower insulation strip 232, an upper wedge-shaped matching rod 233, and a lower wedge. A mating rod 234, a left metal flat plate 235, and a right metal flat plate 236, To the upper insulating strip 231, lower insulating strip 232, upper wedge matched rod 233, lower wedge matched rod 234, left metal flat plate 235, and right metal flat plate 236. The formed form corresponds to the recess waveguide, The center through hole 237 connected to the recess waveguide 1 has a frustum shape, and an outer side of the center through hole 237 of the frustum body is connected to the first transducer 21. Resonant cavity-type recess waveguide microwave chemical plant. The method of claim 1, The adjustable shorting plunger 3 includes a first shorting plunger metal plate 31, a second shorting plunger metal plate 32, a third shorting plunger metal plate 33, a first circular insulating gasket 34, a second A circular insulating gasket 35, a hollow circular tube 36, a metal circular rod 37, a sleeve 38, and a metal flat plate 39, The first shorting plunger metal plate 31, the second shorting plunger metal plate 32, the third shorting plunger metal plate 33, the first circular insulating gasket 34, and the second circular insulating gasket 35 are Spaced from each other, the center of which is fixed to one end of the hollow circular tube 36, the other end of the hollow circular tube 36 is disposed in the sleeve 38, the sleeve 38 being a metal flat plate ( Fixed to the center of 39, characterized in that the metal circular rod 37 is located in the middle of the hollow circular tube 36 and the adjustable shorting plunger 3 can be made of a fixed shorting plate, Resonant cavity-type recess waveguide microwave chemical plant. The method of claim 1, The chemical reactor 4 is made of a low-loss material reactor 41, top cover 42, bottom cover 43, agitator 44, Langmuir probe 45, gas inlet pipe 46 , And a gas outlet pipe 47, The upper cover 42, the gas inlet pipe 46, the lower cover 43, and the gas outlet pipe 47 are respectively located at two ends of the chemical reactor 41, and the exciter 44 is a chemical reactor ( Located in the middle of 41, the Langmuir probe 45 is arranged in the chemical reactor 41 and is fixed on the top cover 42, Resonant cavity-type recess waveguide microwave chemical plant. The method of claim 3, wherein Characterized in that the wedge-shaped mating rod 13 is a dry rod or a water rod, Resonant cavity-type recess waveguide microwave chemical plant. A method for producing ethene from natural gas using the resonant cavity-type recess waveguide microwave chemical plant according to claim 1, The method of producing ethene from natural gas, (1) adopting a resonant cavity-type recess waveguide microwave chemical plant having a working frequency within 0.3 to 22 GHz, wherein the microwave source can adopt continuous or pulsed waves; (2) leaving the resonant cavity-type recess waveguide microwave chemical plant in resonance and the reactor in vacuum; (3) selecting hydrogen gas as an auxiliary gas; (4) adjusting the pressures of the feed natural gas and auxiliary hydrogen gas to 1 to 20 atm and introducing these gases into the reactor through different flowmeters respectively for metering flow rates of different gases; (5) adopting a flow rate ratio of feed natural gas and auxiliary hydrogen gas, that is, a ratio of natural gas: hydrogen gas, from 50: 1 to 1:20; (6) mix feed natural gas and auxiliary hydrogen gas in a gas mixture cabinet and through feed gas inlet 46 and top cover 42 into the quartz reactor 41 of the resonant cavity-type recess waveguide microwave chemical plant; Introducing; (7) The total pressure of the mixed gas in the quartz reactor 41 is adjusted to 1 × 10 ⁻⁴ to 20 atm, and the total pressure of the mixed gas in the quartz reactor 41 is slightly less than that of the supply natural gas and the auxiliary hydrogen gas. Making it lower; (8) power on the microwave source, adjust the microwave output power from tens of watts to several hundred kilowatts according to the auxiliary gas type, flow rate, and pressure of the gas mixture, and discharge the gas mixture in the quartz reactor 41 to Generating a plasma, wherein the discharge condition can be perceived from a Langmuir probe (44) and a cutoff waveguide; (9) thereafter, finely adjusting the microwave output power to obtain the required product, wherein the ethene in the liquid state as the required product can be collected in a condensation trap, Process for producing ethene from natural gas.

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